POS1106 ACHIEVEMENT OF LOW DISEASE ACTIVITY OVER 52 WEEKS IN PATIENTS WITH ACTIVE AXIAL SPONDYLOARTHRITIS ON BIMEKIZUMAB TREATMENT: RESULTS FROM THE PHASE 3 STUDIES BE MOBILE 1 AND BE MOBILE 2
Authors: X. Baraliakos, S. Ramiro, M. Magrey, M. Rudwaleit, N. Haroon, C. Fleurinck, U. Massow, N. De Peyrecave, T. Vaux, H. Marzo-Ortega, V. Navarro-Compán
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Ankylosing Spondylitis (AS) Disease Activity Score (ASDAS) is the recommended instrument to assess disease activity in axial spondyloarthritis (axSpA).<sup>[1]</sup> However, the Bath AS Disease Activity Index (BASDAI) remains commonly used in clinical practice. The recommended treatment target for axSpA is remission or low disease activity (LDA) according to ASDAS levels,<sup>[1]</sup> while limited data exist to validate cut-offs for BASDAI.<sup>[2,3]</sup> However, remission is difficult to achieve for many patients (pts), especially in established disease. Bimekizumab (BKZ) is a monoclonal IgG1 antibody that selectively inhibits interleukin (IL)-17F in addition to IL-17A. BKZ has demonstrated consistent and sustained efficacy up to Week (Wk) 52 in the BE MOBILE 1 and 2 phase 3 studies, including achievement of LDA according to ASDAS by &gt;50% of pts with non-radiographic (nr-)axSpA and radiographic (r-)axSpA (i.e. AS).<sup>[4,5]</sup> <h3>Objectives</h3> To report achievement of LDA, as assessed by either ASDAS &lt;2.1, BASDAI &lt;4, or both, to Wk 52 with BKZ across the spectrum of axSpA in two phase 3 studies. <h3>Methods</h3> BE MOBILE 1 (NCT03928704) and BE MOBILE 2 (NCT03928743) each comprised a 16-wk placebo (PBO)-controlled and 36-wk maintenance period.<sup>[5]</sup> Pts with nr-axSpA in BE MOBILE 1 met Assessment of SpondyloArthritis international Society (ASAS) classification criteria and had objective inflammation as assessed by MRI and/or elevated C-reactive protein. Pts with r-axSpA included in BE MOBILE 2 met modified New York criteria and also fulfilled ASAS classification criteria. All pts had active disease (BASDAI ≥4 and spinal pain ≥4 as per BASDAI item 2) at baseline. Pts were randomised to subcutaneous BKZ 160 mg every 4 wks (Q4W) or PBO; all pts received BKZ 160 mg Q4W from Wk 16 onwards.<sup>[5]</sup> The PBO arm is therefore referred to as PBO up to Wk 16, and PBO/BKZ at later timepoints. Here, we present the proportion of pts achieving LDA to Wk 52, as defined by either ASDAS &lt;2.1, BASDAI &lt;4, or both, using non-responder imputation. <h3>Results</h3> A total of 254 pts with nr-axSpA (BKZ: 128, PBO: 126) and 332 with r-axSpA (BKZ: 221, PBO: 111) were randomised. Most pts had high (ASDAS ≥2.1–≤3.5) or very high (ASDAS &gt;3.5) disease activity at baseline (nr-axSpA: BKZ: 99.2%, PBO: 97.6%; r-axSpA: BKZ: 98.6%, PBO: 100%). In pts with nr-axSpA, a greater proportion of BKZ vs PBO-treated pts achieved LDA at Wk 16 according to ASDAS &lt;2.1 (BKZ: 46.1%, PBO: 19.8%), BASDAI &lt;4 (BKZ: 52.3%, PBO: 31.7%), and both (BKZ: 43.8%, PBO: 19.0%). Separation from PBO was apparent from first post-baseline assessment for ASDAS &lt;2.1 and both ASDAS &lt;2.1 and BASDAI &lt;4 (<b>Figure 1</b>). Results were similar for pts with r-axSpA (<b>Figure 1</b>). Across continuous BKZ-treated pts and PBO/BKZ switchers, achievement of LDA, according to ASDAS &lt;2.1, BASDAI &lt;4, and both, was sustained or improved in both studies to Wk 52 (<b>Figure 1</b>). Proportion of pts achieving BASDAI &lt;4 was consistently higher compared with achievement of ASDAS &lt;2.1, regardless of treatment arm. <h3>Conclusion</h3> Across the full axSpA disease spectrum, dual inhibition of IL-17A and IL-17F with BKZ resulted in rapid achievement of LDA vs PBO to Wk 16, as assessed by ASDAS &lt;2.1, BASDAI &lt;4, or both. Proportion of pts achieving LDA increased to Wk 52. These data suggest that ASDAS &lt;2.1 is a more stringent criteria for LDA than BASDAI &lt;4, and the majority of pts who achieved ASDAS &lt;2.1 also achieved BASDAI &lt;4. This is relevant for the consideration of BKZ in the context of a potential treat-to-target approach for pts with axSpA in daily practice. <h3>References</h3> [<b>1]</b> Smolen J. Ann Rheum Dis. 2018;77:3–17; [<b>2]</b> Kwon OC. Rheumatology (Oxford). 2022;61:2369–74; [<b>3]</b> Chen Y-H. Front Med (Lausanne). 2022;9:856654; [<b>4]</b> Boel A. Ann Rheum Dis. 2019;78:1545–9; [<b>5]</b> Baraliakos X. Arthritis Rheumatol. 2022;74(Suppl 9). <h3>Acknowledgements</h3> This study was funded by UCB Pharma. Medical writing support was provided by Costello Medical, funded by UCB Pharma. <h3>Disclosure of Interests</h3> Xenofon Baraliakos Speakers bureau: AbbVie, BMS, Chugai, Eli Lilly, Galapagos, Gilead, MSD, Novartis, Pfizer, and UCB Pharma, Paid instructor for: AbbVie, BMS, Chugai, Eli Lilly, Galapagos, Gilead, MSD, Novartis, Pfizer, and UCB Pharma, Consultant of: AbbVie, BMS, Chugai, Eli Lilly, Galapagos, Gilead, MSD, Novartis, Pfizer, and UCB Pharma, Sofia Ramiro Consultant of: AbbVie, Eli Lilly, Novartis, Pfizer, Sanofi, and UCB Pharma, Grant/research support from: AbbVie, Galapagos, MSD, Novartis, Pfizer, and UCB Pharma, Marina Magrey Consultant of: AbbVie, Eli Lilly, Novartis, Pfizer, and UCB Pharma, Grant/research support from: AbbVie and UCB Pharma, Martin Rudwaleit Speakers bureau: AbbVie, BMS, Boehringer Ingelheim, Chugai, Eli Lilly, Janssen, Novartis, Pfizer, and UCB Pharma, Consultant of: AbbVie, Eli Lilly, Novartis, and UCB Pharma, Nigil Haroon Consultant of: AbbVie, Eli Lilly, Janssen, Novartis, and UCB Pharma, Carmen Fleurinck Employee of: UCB Pharma, Ute Massow Employee of: UCB Pharma, Natasha de Peyrecave Employee of: UCB Pharma, Thomas Vaux Employee of: UCB Pharma, Helena Marzo-Ortega Speakers bureau: AbbVie, Biogen, Eli Lilly, Janssen, Moonlake, Novartis, Pfizer, Takeda and UCB Pharma, Consultant of: AbbVie, Biogen, Eli Lilly, Janssen, MoonLake, Novartis, Pfizer, Takeda, and UCB Pharma, Grant/research support from: Janssen, Novartis, and UCB Pharma, Victoria Navarro-Compán Speakers bureau: AbbVie, Eli Lilly, Janssen, MSD, Novartis, Pfizer, and UCB Pharma, Consultant of: AbbVie, Eli Lilly, Galapagos, MoonLake, MSD, Novartis, Pfizer, and UCB Pharma, Grant/research support from: AbbVie and Novartis.